What are the diagnostic criteria for Polycystic Ovary Syndrome (PCOS)?

Diagnostic Criteria for Polycystic Ovary Syndrome (PCOS)

PCOS is diagnosed when at least two of the following three Rotterdam criteria are present: (1) oligo- or anovulation, (2) clinical and/or biochemical hyperandrogenism, and (3) polycystic ovarian morphology on ultrasound—after excluding other relevant disorders such as Cushing's syndrome, androgen-secreting tumors, non-classic congenital adrenal hyperplasia, thyroid disease, and prolactin disorders. 1, 2, 3

Clinical Assessment Components

Menstrual History

• Document cycle length, with cycles >35 days indicating chronic anovulation 1
• Persistent oligomenorrhea 2-3 years beyond menarche predicts ongoing menstrual irregularities and greater likelihood of PCOS 4
• Cycle lengths of 32-35 days or slightly irregular patterns (32-36 days) require assessment for ovulatory dysfunction 4

Hyperandrogenism Evaluation

• Assess for gradual onset of hirsutism that intensifies with weight gain (versus rapid onset with clitoromegaly suggesting neoplastic virilizing states) 4
• Look for acne, balding patterns (vertex, crown, diffuse, or bitemporal with frontal hairline loss), and clitoromegaly 1, 4
• Severe acne or acne resistant to isotretinoin carries a 40% likelihood of PCOS 4

Physical Examination

• Calculate BMI and waist-hip ratio 1
• Assess for signs of Cushing's syndrome (buffalo hump, moon facies, hypertension, abdominal striae) 1

Family and Lifestyle History

• Obtain family history of cardiovascular disease and diabetes 1
• Review medication use, including exogenous androgens 1
• Assess diet, exercise, alcohol use, and smoking 1

Biochemical Testing

Androgen Measurement

• Total testosterone (TT) measured by liquid chromatography-tandem mass spectrometry (LC-MS/MS) is the single best initial biochemical marker, with 74% sensitivity and 86% specificity 1
• Calculated free testosterone (cFT) using the Vermeulen equation from high-quality TT and SHBG measurements has the highest sensitivity at 89% with 83% specificity 1
• Free androgen index (FAI) has 78% sensitivity and 85% specificity, but use cautiously when SHBG <30 nmol/L 1
• Androstenedione (A4) has 75% sensitivity and 71% specificity, useful when SHBG is low 1
• DHEAS has 75% sensitivity and 67% specificity, most reliable for adrenal androgen production, particularly valuable in women <30 years 1

Additional Laboratory Tests

• Measure 17-hydroxyprogesterone to exclude non-classic congenital adrenal hyperplasia 1
• Check TSH and prolactin to rule out thyroid disease and prolactin disorders 1

Ultrasound Assessment

Adult Women (≥18 years)

• Follicle number per ovary (FNPO) ≥20 follicles (2-9mm diameter) is the gold standard ultrasonographic marker, with 87.64% sensitivity and 93.74% specificity 5, 1
• Use transvaginal ultrasound with ≥8 MHz transducer frequency for optimal resolution 1, 6
• Alternative markers when accurate follicle counting is impossible: ovarian volume (OV) >10 mL or follicle number per single cross-section (FNPS) 5, 1
• Document three dimensions and volume of each ovary, ensuring no corpora lutea, cysts, or dominant follicles ≥10mm are present 6

Adolescents (<20 years or <8 years post-menarche)

• Do not use ultrasound as a first-line diagnostic tool due to poor specificity and high false-positive rates from normal multifollicular ovaries in this age group 1, 6, 4
• Rely on clinical and biochemical hyperandrogenism plus menstrual irregularity persisting 2-3 years beyond menarche 1, 4

Metabolic Screening

Once PCOS is diagnosed, perform comprehensive metabolic assessment:

• Screen all women with PCOS for type 2 diabetes and glucose intolerance 1
• In obesity (BMI >30 kg/m²), perform oral glucose tolerance testing (OGTT) when fasting glucose is normal 7
• Screen for dyslipidemia with fasting lipoprotein profile (triglycerides, HDL cholesterol) 1, 7
• Measure blood pressure 7

Important Clinical Pitfalls

• PCOM findings alone are insufficient for diagnosis, as polycystic ovaries may be present in up to one-third of reproductive-aged women without the syndrome 6
• The presence of an IUD does not interfere with ovarian imaging, as the IUD sits within the endometrial cavity while ovaries are separate lateral structures 6
• Anti-Müllerian Hormone (AMH) should not replace the Rotterdam criteria for diagnosing PCOS and is not clinically applicable outside research settings until standardization issues are resolved 8
• Ultrasound definition requires at least 12 follicles per ovary measuring 2-9mm in diameter (older criteria) or ≥20 follicles (newer, more accurate criteria) 7, 5
• Rapid onset and severe hyperandrogenism suggest androgen-secreting tumors rather than PCOS 1